Need opinions on gear ratio situation
- Thread starter patmckinneyracing
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Less gear will make the convertor stall/slip at a higher rpm as well as a taller tire.
Did some quick and dirty math using a 225/60x15 tire?????
Should be turning 1800/2000rpm @ 60mph and 2100/2300 @ 70mph.
My guess is your mpg is going away with convertor slippage.
Advancing your cam 4 derees would help also.
Got a tach in the car?
Did some quick and dirty math using a 225/60x15 tire?????
Should be turning 1800/2000rpm @ 60mph and 2100/2300 @ 70mph.
My guess is your mpg is going away with convertor slippage.
Advancing your cam 4 derees would help also.
Got a tach in the car?
As wonderful a thing as an overdrive transmission is, it only affects the compound high gear. In your case, you made a significant change in compound high, going from a 3.73 to a 2.41. An overdrive will not suddenly give you some "Great leap forward" in highway fuel economy beyond that which you would get by going to the same rear gear ratio as the compound ratio you would get from an overdrive. For example, if you ran a TH 200 4R with the 3.73, 3.73 X 0.67=2.49, or only slightly higher than you have now. At a steady state highway speed, this is all that really matters. Yes, you can over do gears and drop fuel economy, but I tend to think that is not the case here. Also, if you do a lot of stop and go during the trip, the 2.41 will adversely affect the fuel economy ( as will the Edelbrock carb vs a Q-Jet) since wheel torque per throttle opening percentage will be lessened. One thing you didn't say is if you are running a vacuum advance on your distributor. Not having it hooked up will negatively affect fuel economy too. I will also say that a change in fuel formulation may be affecting it too. The EPA is mandating more ethanol as an oxygenating agent in some places, and this can lead to a drop in fuel mileage. I have noticed this in my local area over the last year or so as both my running cars have lost a significant amount of fuel mileage due to the reformulation of local gas supplies. Why is this so? Well, ethanol has significantly fewer BTU's of energy per given volume of fuel, thus requiring the use of more fuel to achieve similar power levels. Remember that the stoichiometric mix of normal gas to air is 14.7:1 while ethanol requires a much richer 9.9:1 mix.
My gearing right now is a 3.23 with the TH 200 4R overdrive. The compound high is 2.14:1. This lets me have the better gearing to get me off the line with less throttle input in traffic, but still lets me have reasonable steady state fuel economy too. My engine is set to have a torque curve that begins in earnest around 1800 RPM, so it is about ideal for my situation. However, I do wish I had a manual transmission because I can see where the converter slippage hurts things on the tach. As for the rest of the combo, most of it is tuned for fuel economy. The Quadrajet is like having a 200 CFM 2 barrel almost all of the time. The secondaries do not come in to play until you really step on it. The same is true of your Edelbrock, but it drives like a 300 CFM 2 barrel most of the time because it is a square flange carb. What is the difference? Well, the smaller venturis in the Q-Jet have a stronger vacuum signal at a lower RPM and can thus run a slower idle speed. They also make the engine more efficient as they produce more torque at part throttle than a bigger carb can.
My gearing right now is a 3.23 with the TH 200 4R overdrive. The compound high is 2.14:1. This lets me have the better gearing to get me off the line with less throttle input in traffic, but still lets me have reasonable steady state fuel economy too. My engine is set to have a torque curve that begins in earnest around 1800 RPM, so it is about ideal for my situation. However, I do wish I had a manual transmission because I can see where the converter slippage hurts things on the tach. As for the rest of the combo, most of it is tuned for fuel economy. The Quadrajet is like having a 200 CFM 2 barrel almost all of the time. The secondaries do not come in to play until you really step on it. The same is true of your Edelbrock, but it drives like a 300 CFM 2 barrel most of the time because it is a square flange carb. What is the difference? Well, the smaller venturis in the Q-Jet have a stronger vacuum signal at a lower RPM and can thus run a slower idle speed. They also make the engine more efficient as they produce more torque at part throttle than a bigger carb can.
I'm running 215/60r15 on all 4 corners. The timing is currently set at 11.5 degrees in park just sittin. The only reason I would want an overdrive transmission is so that I could put my 3.73's back in. Currently, I'm checking the valve train cause ever since the car over heated on me that one time when the clutch fan went out, there has been some knock coming from inside the valve cover. Even my oil pressure went to sh**. At Idle I'm getting 10lb. and when I rev or am on the high its sittin at roughly 22lb.
85 Cutlass Brougham said:
Yes, but if part of his problem is convereter slippage, as some have suggested, an overdrive transmission with a lockup converter would eliminate the slippage.
Yes it was an issue when I made that trip. I had to drive it again with the same problem 3.5 hours to get back here yesterday. I have a feeling that either my valve guides are bad or I have a collapsed lifter. I took off the valve cover and checked what was visible but everything looked good on the top end. The oil pressure remains at 22lb. on the highway.
I just took out a small loan to buy a daily driver so I'm not having to beat the hell outta of my malibu going back and forth long distances. Looking at buying one of those early 90's small nissan pickup.
I just took out a small loan to buy a daily driver so I'm not having to beat the hell outta of my malibu going back and forth long distances. Looking at buying one of those early 90's small nissan pickup.
if the engine has mechanical issues then I don't think you can compare the fuel mileage of different gear set ups...
To me, it sounds like you have a bad bearing, or one that is damaged from the overheat. That is why the oil pressure has gone down. As for buying a Nissan pickup, I have to agree with you on that. Just be sure to get a 4 cylinder 5 speed as the V6 is not as good as the 4, and the manual is much more reliable than the automatic. The D22 Frontier is essentially the same underneath as the D21 Hardbody, but it has the more powerful DOHC version of the KA engine and does not have as much of a potential timing chain issue as the SOHC version. The D22 also has larger front and rear brakes off the 4x4 Pathfinder. It's one of the most robust vehicles you will ever buy, and mine has lasted an incredible amount of miles on most of it's original parts. I now have over 330k on it and have yet to change items like the master cylinder or clutch hydraulics. I even got almost 300k out of the original starter in a vehicle that has been used since day one for delivering pizza.
I don't think a bad bearing would have lasted the 3.5 hour drive. As for the oil pressure if it's a bad bearing the needle usually jumps a few pound back and forth, at least it has in motors I've had with a bad bearing just before they grenaded...I'm thinking he's damaged something in the valve train.....There's only two ways of finding out whats wrong tho, either rev the piss out of the engine till it blows up or tear it down
I overheated the engine a few times that I just took out of my car but I was running synthetic oil which saved the day...actually it was a few days....I'll never run conventional oil no matter what I'm driving
I overheated the engine a few times that I just took out of my car but I was running synthetic oil which saved the day...actually it was a few days....I'll never run conventional oil no matter what I'm driving
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